RV, off-grid and 12V systems

What Changes When an RV's Victron MultiPlus-II Goes From Shore Power to Battery?

Published · By the SolarPanelX editors · Prices and specs as of that date, from the pages under Sources

Summary

On shore power or a generator, the U.S. MultiPlus-II 2x120V passes that AC straight through to the RV's loads and charges the battery at the same time. When the outside source goes away, it switches to inverter mode and puts out 120 V only. Victron's manual says 240 V loads run only while a split-phase 120/240 V source is connected.

Plugged in

The AC input current limit can be set anywhere from 9.5 to 50 A, so it can be turned down to match the breaker on a campground pedestal. When loads ask for more than that, PowerAssist makes up the difference from the battery. In the manual's own example, PowerAssist adds up to 3 kVA (25 A at 120 V) to output L1, and with a 50 A input the output can supply up to 75 A. Battery charging draws from L1, and the 12/3000 model charges at up to 120 A.

The manual is inconsistent on the starting value for that limit: its default-settings table says 50 A, while the section on the current limit, on the same page, says "Factory setting: 30A."

Unplugged

With the UPS feature on, which is the default, the unit moves to inverter operation practically without interruption when AC input fails. In inverter mode it ties L1 and L2 together and feeds 120 V to both, so 240 V loads get nothing. Victron presents this as a way to stop heavy loads such as water heaters or 240 V air conditioners from draining the battery. Anything on the AC-out-2 terminal is disconnected the moment the unit goes to battery and reconnected about two minutes after outside power returns.

Continuous output falls as the surroundings heat up. For the 12 V, 3,000 VA model (12/3000/120-50):

Ambient temperatureContinuous output
25°C (77°F)2,400 W
40°C (104°F)2,200 W
65°C (149°F)1,700 W

Peak power is 5,500 W. Victron's April 2024 RV brochure builds an example system around the same 12/3000 (a SmartSolar MPPT 100/50, two 12.8 V 200 Ah batteries for 5,120 Wh, an Orion XS DC-DC charger, and up to 700 W of solar) and labels it "6000W Peak," which does not match the 5,500 W in the spec table.

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Sources

  1. Victron Energy — MultiPlus-II 2x120V manual, Technical specifications
  2. Victron Energy — MultiPlus-II 2x120V manual, Description
  3. Victron Energy — MultiPlus-II 2x120V manual, Configuration
  4. Victron Energy — MultiPlus-II 2x120V manual, Installation
  5. Victron Energy — RV brochure (USA, REV00 2024-04)

We have not tested these products. Specs, prices, stock and terms are as published on these pages on the date above and can change; check the manufacturer or retailer before you buy.

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